水文过程对农业小流域氮素迁移的影响

以江西低丘红壤区农业小流域为研究对象,在自然降雨条件下对小流域内试验小区、上游灌渠和小流域出口径流中的氮素浓度进行监测,旨在从小区尺度和小流域尺度阐明农业小流域氮素流失与降雨和径流的关系。结果表明:在小区坡面流中,硝态氮浓度随降雨径流的变化趋势不明显,铵态氮和全氮浓度随降雨径流的增加呈先增加后降低的趋势;壤中流对硝态氮的流失有主要影响,而坡面流对全氮的流失作用不可忽视。小流域的氮素流失主要发生在4~6月,其间氮素NH4 -N、NO3--N和TN的流失量在上游干旱地灌渠分别占年流失量的74%、61%和62%;在小流域出口分别占年流失量的82%、70%和79%。年全氮流失量达43.8kg/hm2,占氮素施用量的22.6%。

Effects of hydrological factors on nitrogen loss in small agricultural catchments

Soil nitrogen loss processes resulted from rainfall and runoff were monitored in a small agricultural catchment of red soil areas in Jiangxi Province with the aim to investigate the relationship between the soil nitrogen loss and the corresponding rainfall and runoff.The results show that the concentration of NH~ _4-N and total nitrogen in the overland runoff is high in the beginning of rainfall and runoff,and then decreases rapidly with rainfall and runoff,the concentration of NO~-_3-N shows no appreciable change.Surface runoff have an important influence on the total nitrogen loss and subsurface runoff affect the nitrogen loss.The nitrogen loss mainly occurs in April to June.In the upstream dry field,losses about 74% of annual loss for NH~ _4-N,61% for NO~-_3-N and 62% for total nitrogen take place in this period.At the basin mouth,the relevant figures were 82%,70% and 79% respectively.The annual total nitrogen loss is up to 43.8kg/hm~2,which accounts for 22.6% of nitrogen fertilized by farmers.